I have to say that in 3 years that I have only had two people ask me about the nocks so I havent't heard of any problems with any of them other than that.
I typically shoot white nocks but have ocasionally shot the translucent orange and green without any problems. Yes, I have broken a few, but only after hitting very hard objects. Infact, I would have normally expected some of those hits to produce broken arrows.
Now I can only account for 10 + doz. arrows over the last couple of years (I don't like looking for lost arrows), but I also exclusively shoot bows in the 80lb + range. The nocks are the same for all size shafts too.
This is not to say that there hasn't been an issue, I have only had a couple of customers contact me about broke nocks and I sold nearly 3000 doz arrows last year.
thanks, bigjim